Sharks are the oldest predators that appeared on the planet 450 million years ago. They haven't changed much since then. Sharks are one of the few living things that cause the greatest fear in humans in their lives.
Instructions
Step 1
Most sharks have an elongated and spindle-shaped body. Their skin color depends on the type of fish itself and can be blue or gray, even white (white shark). Some sharks are generally colored with spots or stripes (for example, the tiger shark). Their head has a peculiar elongation in the form of a nasal outgrowth, which is called the rostrum. On the sides of the shark's head, there are gills - several slits through which oxygen-enriched water passes. In ancient species of sharks, these crevices are usually 5 pieces on each side, and in modern ones - up to 7 pieces. Shark eyes are black and large. They are located on the sides of the head. Two holes can be seen behind the eyes leading to the pharynx. Ichthyologists call them squiggles, representing the rudiments of the gill slits.
Step 2
Curiously, there is not a single real bone in the shark's body. Their skeleton consists entirely of cartilage, and the skin of most representatives of these formidable predators is covered with rather sharp spines. It is worth noting that the inhabitants of some islands and peninsulas use this shark skin as a grinding material for polishing wood. The paired limbs of sharks are pectoral and pelvic fins that are horizontal. The tail fin is of different layers, and its shape differs in different shark species. This is due to the certain living conditions of this or that species of these fish. It is worth noting that sharks are fish that do not have a swim bladder. Other organs compensate for negative buoyancy: an enlarged liver, fins and cartilaginous skeleton.
Step 3
Shark mouths are located at the bottom of the head. This is not very convenient for the fish itself: in order to grab its prey, it has to turn on its side or even on its back. The teeth of most of these creatures are very large, sharp and serrated at the edges. They are tapered. A distinctive feature of the jaws of all sharks is the non-standard arrangement of the teeth: they are located in five (or even seven) rows. In addition, the teeth of these fish are easily regenerated in case of breakage for six times in a lifetime.
Step 4
Sharks are found in almost all oceans and seas of the planet. These fish are the oldest on Earth. Currently, there are more than 450 species of them - and these are far from all species known to science. Sharks are very voracious fish, there is even a saying: that a wolf is on land, then a shark is in the water. Many of these fish swim in whole schools after ships and ships, expecting that something edible and not so much will fall into the water. The fact is that they can swallow everything: cans, empty bottles, and other trash. If we talk about record-breaking sharks, then the smallest shark in the world is recognized as a deep-sea one, its body length is only 17 cm, and the largest is a harmless whale shark with a body length of 20 m.
